Swansea City have been a real surprise package this season, though I had a feeling they might shock a few people after watching them in the Championship play-off final in May. Having seen their opponents that day, Reading, beat Everton in the FA Cup earlier in the year, I felt that there would only be one winner at Wembley. But Swansea blew Reading away - they were strides ahead of where I expected them to be and they have certainly carried that belief into their first few months in the Premier League.

On Saturday, they welcome Manchester United to the Liberty Stadium in front of the ESPN cameras and this will be a real acid test to determine just how far they have come. It has been refreshing to see that, so far, all the promoted clubs have been looking to follow the example of Blackpool last season by stepping up and showing a real desire to play good football, rather than just be long-ball battlers. Swansea pass it well, have a great team ethic and they've got loads of pace.

One Swansea player in particular who boasts speed in abundance is Scott Sinclair. He's one of a number of lads at the club who are hungry to perform in the top flight having been released by Premier League clubs earlier in their careers. They include Neil Taylor, who was at Manchester City, Alan Tate was at Manchester United, Leon Britton was at both Arsenal and West Ham, and Sinclair, of course, was at Chelsea until just last year.

Although at the time it never seems good, rejection can be a good thing if you react in a positive way. I went to Coventry as a kid, got picked out of a trial involving 200 boys with another lad and then I was let go. Rejection early on can be a great spur - it was for me and I'm sure it will be for Scott Sinclair and all those players who were released. Unfortunately, there's no way that the big clubs can keep all these players on their books and it's always the young ones that are let go, because they want to bring in players who already have the experience.

I think Scott is proving now that dropping down to the Championship to cut his teeth was a good idea. Some players develop physically earlier than others - Wayne Rooney is a prime example of that, at 15 he was like a 22-year-old. Then there's some who at 19 might not be quite there physically but they suddenly develop and come into their own. I think Scott Sinclair has done that. Now he has all the ingredients to be a top Premier League player. He's no headless chicken and has a good footballing brain to go with that explosive speed; he's also not afraid to challenge people and, perhaps most importantly, is not afraid to take players on and get past them. I think there's every chance Chelsea could be left regretting their decision to let him go in the future.

While Sincair has been impressive, there has been one player at Swansea who has truly stolen the spotlight so far this season: goalkeeper Michael Vorm. He had a baptism of fire in that first game against Manchester City but if he hadn't been there then it would have been much more embarrassing than a 4-0 scoreline; some of his saves in the game were unbelievable and at £1.5 million he looks incredible value for money. He's another Dutch goalkeeper doing well in the Premier League, with Tim Krul up at Newcastle also establishing himself as one of the division's most consistent No. 1s; both of them I'm sure will be looking to follow the example of a certain Edwin van der Sar, who was a giant between the posts for Manchester United.

It's one of the great things about football that for all the massive transfers and the millions and millions of pounds spent, sometimes the smaller clubs can pull out a signing that can define their season. It shows how clubs like Swansea have to think differently - there are so many really good players out there who aren't necessarily playing for big teams and won't cost a fortune. It's probably the best money they've spent and, if Swansea stay up come next May, Vorm will have unquestionably played a major role; in fact, he already has.

The goalkeeper alone cannot claim all the credit, though, as Swansea's whole backline has been rock solid since that opening defeat to City. Their defensive record is probably what's surprised most people as, after that first game, people looked at them and thought 'Swansea cannot survive in the Premier League'. They've become much more streetwise since then and credit to the manager and the coaching staff for assembling such a well-organised unit. They have only conceded one goal at home but with the greatest respects to their opponents so far - Wigan, Sunderland, West Brom, Stoke and Bolton - Manchester United will be a different proposition altogether.

I'm sure Brendan Rodgers will be hoping that United field a weakened team but I think Sir Alex Ferguson knows he cannot afford to take any risks with his selection. He is going to Wales knowing that a win is necessary to keep the pressure up on Man City and, historically, Man United go to places like Swansea and take all three points. It's not always easy, as we saw when Blackpool should have won last season when they played really well, but United have this knack of grinding out a result and somehow getting the win they need.

Wayne Rooney will of course be raring to go after having a break for the internationals and it will be interesting to see where Phil Jones plays after two impressive performances from England in central midfield. I think he's the sort of player who can play anywhere because he's got a fantastic attitude; he can be a right-back, centre-half, central midfielder and I'm sure that even if Patrice Evra got injured, Sir Alex would be happy to play him at left-back as he knows that he won't let him down.

Phil can pass it well, he's got decent pace, very good strength and if you stick him in midfield, along with two big centre-backs behind him, it gives you great height when defending and attacking set-pieces, which is a major asset. We had Sam Allardyce on ESPN last year and he said after only a few games in the first team at Blackburn he could tell that that Phil was top, top quality. His performances for Manchester United definitely won't have surprised anyone at Ewood Park. I didn't have the pleasure of seeing Duncan Edwards play but when I was young he was the player who everyone talked about as one of the greatest - Phil has already been mentioned in the same breath as him, which shows that people at Manchester United know that he's destined to be at the top for a long time to come.

Whether Swansea will be in the top division for a long time to come remains to be seen, but the time to judge them as a Premier League outfit, and see exactly where they are, will come when the final whistle goes on Saturday evening. There's always a chance of an upset in the Premier League and, while I don't think it will happen this time, if it does I will be the first to hold my hands up and say that, aside from Manchester City's win at Old Trafford, we will have witnessed the biggest upset this season.

Kevin Keegan is ESPN's Lead Football Analyst ESPN analyst Kevin Keegan is one of English football's most respected figures and he will be writing for ESPN throughout the season. As a player, Kevin represented Liverpool with distinction, winning numerous titles in domestic and European football, and was twice named European Footballer of the Year during his time at Hamburg. Kevin managed England, Newcastle United, Manchester City and Fulham.